2x15 Help?

[owmallon]

I recently purchased two Sunn 2x15 cabinets with JBL D140F at 8 ohms along with a Sunn 200s head. I am planning on running  one cabinet through the Sunn 200s and the other through an Ampeg SVTAV. I am having a hard time finding specs for the cab, so I am nervous about blowing one of them with a 300 tube watt SVTAV. Do you think I am ok?

P.S. - I am relatively new to Sunn so please do not afraid to be straightforward and obvious

Thanks

[tabasco]

What ohm is your Ampeg head? Are the JBL's 8ohm or 16 ohm (each individual speaker), so I can tell ya how to wire them for the best performance. Off the top of my head I would say your JBL's could handle more than ya got! Great speakers if they are in good shape.

[owmallon]

The Ampeg head has a selector between 2 and 4 ohms and the JBL's for each speaker are 8 ohms

[basiklybass]

Personally, I'd be careful with the Ampeg head into 2 D-140F's, especially if they have never been reconed by a professional. The newer recone kits (K & E series) can handle morepower than the D's. Aftermarket kits sometimes handle even more.
The Sunn head is 60 watts and should not stress the speakers...but playing a bass through an amp is not like playing music or a guitar. The transients are much greater. I would be very careful. If they were K's or E's, I'd say no problem...but D's....IMHO

[owmallon]

This is the set up. I also have an Ampeg 8x10, but I am trying to downgrade to save space and money

[EdBass]

That SVT (what is an SVTAV?) has the capacity to disembowel those D140F's.

What ohm is your Ampeg head? Are the JBL's 8ohm or 16 ohm (each individual speaker), so I can tell ya how to wire them for the best performance. Off the top of my head I would say your JBL's could handle more than ya got! Great speakers if they are in good shape.

Ohms don't have anything to do with it. Heads don't have "ohms", ohms is a measurement of resistance or impedance to current flow. Tube heads have transformers to match ohms with drivers, but they couldn't care less how the cabinet is wired how many ohms the load is as long as the impedance matches.

I run a Sonic I40 (one D140F) with a new Reeves Amplification Custom 225 for practicing, as long as you are real careful with the volume it will hold up just fine, but I could gut the JBL with a little twist of the master volume. If you start pounding your 200S with that big Ampeg, get it growling real good, those D140F's will decone themselves.

[tabasco]

Well I guess all the amp makers out there have it all wrong and are mis leading there customers telling them there is a different Wattage output  depending on what Ohm load they are playing through. I am not an electrician, just been playing bass for 50 or so years and from my experience I have found that Ohms or load problems can fry your head and wattage can dust your speakers. The boy said he had a 300 watt head, I ran 600 watts in the 70's and 80's daily and blew out 2x15 radio shack, eminence, Utah, and probably a few more brands I cant remember. Then I got 2 JBL D140F  8 ohm 15 inch speakers rated I think at 150w RMS 400 peak each. Guess what, still got them and never blew another speaker. I guess experience  does not  have a chance with all the knowledge on this site. No balls no glory! 

[JoeArthur]

Well I guess all the amp makers out there have it all wrong and are mis leading there customers telling them there is a different Wattage output  depending on what Ohm load they are playing through. I am not an electrician, just been playing bass for 50 or so years and from my experience I have found that Ohms or load problems can fry your head and wattage can dust your speakers. The boy said he had a 300 watt head, I ran 600 watts in the 70's and 80's daily and blew out 2x15 radio shack, eminence, Utah, and probably a few more brands I cant remember. Then I got 2 JBL D140F  8 ohm 15 inch speakers rated I think at 150w RMS 400 peak each. Guess what, still got them and never blew another speaker. I guess experience  does not  have a chance with all the knowledge on this site. No balls no glory! 

Experience in the absence of knowledge doesn't benefit anyone. 

If you are interested in expanding your knowledge of this subject, this is a good place to start. It's a down to earth and easy to understand explanation of some of the many problems with loudspeaker design.

http://www.peavey.com/support/technotes/hartley/chapter_2.pdf

On the other hand, you will be greatly loved by many manufacturers placing your faith (and money) in their specifications instead of dealing with all of that messy knowledge stuff.  I guarantee.

[Soundmasterg]

The manufacturers will often find tricky ways to rate their products so it appears that they are better than a competitor's, and JBL was no exception. The D140 might have been listed as a 150 watt speaker, but it was more like a 100 Watt speaker, and if you ask Ted Weber, he would probably rate them more like 80 watts. The speakers are rated at a given impedance level, not resistance, and impedance varies with frequency, so the power output and volume and tone of a speaker will vary with frequency. If you want something that doesn't do this, then plug into a resistor. The vintage JBL's are great speakers, but aren't the holy grail and can't do things they are not designed to do. A tube SVT of 300 watts will destroy a set of D140's in a matter of minutes if the volume is loud enough. That 300 watts RMS is rated before the onset of distortion, which on an SVT would be somewhere around 3 or 4 on the volume dial. If it was my speakers, I wouldn't try it unless I was playing very quietly.

Greg

[JoeArthur]

The manufacturers will often find tricky ways to rate their products so it appears that they are better than a competitor's, and JBL was no exception. The D140 might have been listed as a 150 watt speaker, but it was more like a 100 Watt speaker, and if you ask Ted Weber, he would probably rate them more like 80 watts. The speakers are rated at a given impedance level, not resistance, and impedance varies with frequency, so the power output and volume and tone of a speaker will vary with frequency. If you want something that doesn't do this, then plug into a resistor. The vintage JBL's are great speakers, but aren't the holy grail and can't do things they are not designed to do. A tube SVT of 300 watts will destroy a set of D140's in a matter of minutes if the volume is loud enough. That 300 watts RMS is rated before the onset of distortion, which on an SVT would be somewhere around 3 or 4 on the volume dial. If it was my speakers, I wouldn't try it unless I was playing very quietly.

Greg

Well obviously Greg <sigh> - an ex-spurt like "Ted Weber" is going to have much better knowledge of JBL D140F power ratings than anyone fresh off the street... like say, a "Harvey Gerst". 

Oh... an SVT has 300 "tube" watts? Dang, I forgot about that - I though they were ordinary watts. 

"That 300 watts RMS is rated before the onset of distortion" 

Sorry... I can't resist - I REALLY NEED A LINK for your "BEFORE the onset of distortion" qualification for the measurement of the power output of an SVT ("tube" or otherwise... wattage measurement). 

Thank you in advance.

[EdBass]

Well I guess all the amp makers out there have it all wrong and are mis leading there customers telling them there is a different Wattage output  depending on what Ohm load they are playing through.

No argument about that statement, but....
Transistor amps vary output by impedance, tube amps (such as the SVT being discussed in this thread) do not. However, even solid state amps don't have "ohms", i.e.;

What ohm is your Ampeg head?

Again, ohms are a measure of resistance/impedance and do not correlate to an amplifiers output other than the effect the load (which is rated in “ohms”) has on the output potential. A solid state amp can be rated for X watts at a specific load, a load measured in ohms, but an amp is not rated as being any specific “ohms”. Tube amps output (pretty much) the same watts at any impedance, but you need to match the load impedance with the output stage impedance using a transformer. That’s why most tube amps have switchable transformer taps, as in the selector on an SVT for either a 2 or 4 ohm speaker load.

I am not an electrician, just been playing bass for 50 or so years

Man, you are OLD.

I have found that Ohms or load problems can fry your head and wattage can dust your speakers.

Anyone who has messed around with amps long enough know that smell, some of us delve into why these thing blow up.

The boy said he had a 300 watt head, I ran 600 watts in the 70's and 80's daily and blew out 2x15 radio shack, eminence, Utah, and probably a few more brands I cant remember.

Even cheap speakers will take an incredible amount of clean sine wave; it’s when your power amp starts clipping that the fireworks begin. Clipped tube amps are much friendlier to speakers than clipped transistor amps, tube distortion could be described as “warm”, and transistor distortion is much harsher.

Then I got 2 JBL D140F  8 ohm 15 inch speakers rated I think at 150w RMS 400 peak each. Guess what, still got them and never blew another speaker.

I'm a HUGE fan of D140F's for bass, and have used them since they were available new. However, they are not capable of handling power on the scale of modern drivers; way less than 600 watts can blow the cones off of a pair of D140F’s.
What kind of amp(s) were you using?
You either were not pushing your amp(s), or maybe they were solid state and the JBL’s were configured to show a 16 ohm load. If your amp(s) (I don’t remember any mono 600 watt MI amps in the olden days) outputted 600 watts into a 4 ohm load,  at 16 ohms you could be making as little as 150-175 watts, well within the tolerance for a pair of D140F’s.

I guess experience does not have a chance with all the knowledge on this site. No balls no glory! 

Just hang in there, I for one believe that an old dog can indeed learn new tricks. This forum is mostly pretty friendly .

[tabasco]

Edbass, My Brains were custom made by a guy that I just can't remember his name in Downey California, Yes I am old. He lived and worked in a electronic store called Net electronics on Firestone Blvd. Wow blast from the past! I know I made a mistake on the way I worded the question on ohms of the amp. I was not familiar with the amp head he was describing and should of asked 300 RMS or 300 peek. Yes I was asking about the ohms of the JBL's and how his cab was wired so I could give him a choice on how much power he was going to put through the speakers. I believe unless you got pockets of money you should try to use what you got if it gets the job done, and you get a paycheck at the end of the gig. Also I read the Peavey article that Joe Arthor suggested and got a chuckle on the last page were it says “EXPERIENCE IS THE GREAT TEACHER”
I agree.

[JoeArthur]

Sorry, can't let this go. 

Transistor amps vary output by impedance, tube amps (such as the SVT being discussed in this thread) do not.

Not true - both tube and solid state amps vary their output power based on the impedance of the load - the instantaneous value of the load impedance, NOT the "nominal" impedance rating.

Despite what some may believe, even tube amps do not violate Ohm's law.

However, even solid state amps don't have "ohms", i.e.;

What ohm is your Ampeg head?

Again, ohms are a measure of resistance/impedance and do not correlate to an amplifiers output other than the effect the load (which is rated in “ohms”) has on the output potential. A solid state amp can be rated for X watts at a specific load, a load measured in ohms, but an amp is not rated as being any specific “ohms”.

This is the start of a circular argument.

Tube amps output (pretty much) the same watts at any impedance, but you need to match the load impedance with the output stage impedance using a transformer. That’s why most tube amps have switchable transformer taps, as in the selector on an SVT for either a 2 or 4 ohm speaker load.

And this directly contradicts the circular argument you started above.

Ohms is simply a quantity of measurement, just the same as "Watts" is a quantity of measurement.

Question: If a tube amplifier doesn't have an "Ohms" output then what exactly is being matched by those switchable transformer taps? Answer: The output impedance of the amplifier to the load impedance.

Both impedance values are measured in Ohms. So, if an amplifier has an output impedance there would have to have some specific "Ohms" measurement to that impedance. Doesn't matter if you call it a rating or not, there is still an ohms measurement for the output impedance of the amp.

Obviously... I am totally confused what point you are trying to make. Chalk it up to old age.  But if you used new D140F's... you ain't no spring chicken either!! 

[basiklybass]

Haa...great discourse from my favorite writers .

I agree, there were not many (if any) amps in the early to mid 70's that were rated at 600 watts. Crown had just come out and they were getting more powerful....but I can't recall seeing any mono 600 watt amps back then (yep, I'm kinda old too! ) I do know there was a Kalamazoo with 1 10" that a guy brought over in 1971 and it said it was 80 watts or something like that. Peak Music Power. If I recall correctly....PMP was something like 3 or 4 times RMS. I currently have a Yamaha DMX660 PA combo that they claim is 300 watts a channel...yet the draw is only 158 watts. Point being: what some claim to be putting out....is like that story we all used to tell about our dates...we said they did....but mostly they didn't. I would be cautious using 4 - D140's with an SVT...2 would be very scary.

Then again, I see some guy proudly proclaiming he is using 2225 voice coils with 2226 cones and making his E 140’s 400 watt speakers. Who knows, the 2225 coil fits the D140’s as well…maybe someone made those 140’s into super 140’s……

I stand by my original post: be careful and don't turn up too much.